KR101150285B1 - Water purification membranes with enhanced antifouling property and manufacturing method thereof - Google Patents

Abstract

The separator for water treatment of the present invention comprises the steps of: 1) preparing a dope solution by mixing a polyvinylidene fluoride-based or polysulfone-based film-forming polymer and a polyoxazoline-based polymer as a first additive in a solvent; 2) applying the dope solution onto the porous support; And 3) preparing a hollow fiber membrane or a flat membrane by contacting the porous support on which the dope solution is applied to an external coagulation solution. It includes.

As a result, the first additive has a plurality of micropores in the portion other than the macropores and macropores having the skin layer and the micropores nanosponge layer formed by containing a plurality of nanopores in the portion other than the micropores and the micropores having the skin layer. Water permeability and rejection rate can be simultaneously improved by playing a role of inducing the creation and expansion of the macroporous nanosponge layer formed by including the nanopores. In addition, the first additive suppresses the aggregation of the spherical particles, thereby maintaining excellent water permeability and fraction molecular weight, and the hydrophilicity due to the strong interaction between the membrane-forming polymer and the first additive is maintained throughout the membrane. In spite of long-term operation, water permeability does not decrease and pollution resistance can be greatly improved.

Water Treatment Membrane, Pollution Resistance, Additives, Phase Inversion

Description

Separation membrane for water treatment with excellent pollution resistance and its manufacturing method {WATER PURIFICATION MEMBRANES WITH ENHANCED ANTIFOULING PROPERTY AND MANUFACTURING METHOD THEREOF}

The present invention relates to a separation membrane for water treatment and a method for producing the same having excellent fouling resistance, and more particularly, to prepare a dope solution containing a polymer, a solvent and an additive and to apply the dope solution on a spinning or support and The present invention relates to a porous membrane and a method of manufacturing the same, comprising the step of contacting a support coated with a spinning solution or a dope solution to an external coagulation solution to produce a hollow fiber membrane or a flat membrane.

Membrane separation technology is an advanced separation technology that can almost completely separate and remove the material to be treated in wastewater or purified water according to the pore size and membrane surface charge of the membrane.It can produce high quality drinking water and industrial water in the water treatment field. Its application range is increasing, including advanced treatment and reuse of sewage water and clean production processes related to the development of zero discharge systems, and it is becoming one of the key technologies that will attract attention in the 21st century.

Membrane manufacturing is usually performed by phase inversion method using high molecular phase separation by mutual diffusion between solvent and non-solvent for polymer, and membrane using membrane since membrane inversion method was introduced in 1960. The separation process is becoming one of the new advanced separation technologies. As is well known, porous membranes have pores ranging in size from tens of nanometers to tens of micrometers based on the variety of materials, and are used for separation and concentration of a wide range of materials including gas separation and wastewater treatment. It is believed that its use will gradually expand in the future because of its merits. This phase inversion method allows the production of membranes applicable to various fields such as water treatment, blood purification, etc. by providing an advantage of controlling the pore size of the porous structure in a variety of ways, but there are various control variables and complex problems. As an alternative to the phase inversion method, a membrane production method using heat-induced phase separation has recently been introduced. The so-called TIPS process is a method of crystallization of polymers by uniformly dissolving crystalline polymers and diluents at high temperatures and lowering them to low temperatures. Formation of porous structure through solid-liquid phase separation and extraction of diluent is mainly used for forming nylon, polypropylene, and polyethylene porous membrane.

However, despite the development of such membrane structure, the problem of water permeability reduction due to membrane contamination is still an obstacle to overcome. This is because most commercially available water treatment membranes are hydrophobic polymer materials such as polyvinylidene fluoride and polysulfone. Because it is composed of. Therefore, various attempts have been made to improve hydrophilicity by imparting hydrophilicity to such membrane materials. For example, in Korean Patent Publication Nos. 2004-0101853, 2004-0100750 and 2004-0089886, polyvinylpyrrolidone and silica or titania inorganic nanoparticles, which are hydrophilic polymers, are coordinated in a sol state, and then these hybrid materials are poly-linked. An example of a separation membrane prepared by mixing a vinylidene fluoride polymer solution to prepare a porous membrane or simply coating or blending a tinania sol on a polysulfone water treatment membrane formed previously is disclosed. In addition, Korean Patent Publication No. 2005-0100834 discloses a method of manufacturing a hollow fiber membrane having antimicrobial properties by immersing the hollow fiber membrane formed before the drying step in a coating solution containing an organic antimicrobial agent and a crosslinking agent and then crosslinking the same with ultraviolet rays. Patent Publication No. 2007-0017741 discloses a preparation example of a separator prepared by dissolving metal nanoparticles such as Ag, Au, Fe in a low concentration polyvinylpyrrolidone solution, reducing them through UV irradiation, and then mixing them with a polymer solution. It is starting.

However, conventional methods involve additional processes, such as making inorganic particles nanoscale and coating or using ultraviolet radiation to reduce the particles to metal. In addition, in order to uniformly disperse these inorganic nanoparticles in the film-forming polymer, a procedure such as pre-dissolution in a hydrophilic polymer such as polyvinylpyrrolidone and mixed with the film-forming polymer is carried out. However, the polyvinylpyrrolidone can provide hydrophilicity to hydrophobic polymers by simple mixing, but it is well known that the introduction of polyvinylpyrrolidone generally reduces the average porosity to reduce the water permeability. (Macromol. Res ., 14, 596 (2007), J. Membr. Sci., 211, 139 (2003)).

In the case of a separator that does not use an additive according to the present invention, referring to FIG. 1 added, the surface layer 100 formed on the separator surface, the microporous support layer 150 including micropores, and a plurality of aggregated particles are described. It consists of a spherical particle support layer 400 containing. The separator has a problem in that the pores are not sufficiently developed and formed due to its structure, so that the water permeability and rejection rate are low and the pollution resistance is not good.

Accordingly, the present inventors mixed the poly (oxazoline) -based additives with polyvinylidene fluoride-based and polysulfone-based polymers in order to solve the conventional technical problems, and produced a porous membrane by a phase inversion method. In addition to improving the permeability and fractional molecular weight, the hydrophilicity was maintained, and thus, a water treatment membrane having improved fouling resistance was obtained, which does not reduce water permeability even during long-term operation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing a porous water treatment membrane having improved water permeability, BSA excretion rate and fouling resistance as it includes a membrane-forming polymer and a polyoxazoline-based polymer as a first additive.

It is still another object of the present invention to provide a porous water treatment membrane having improved water permeability, BSA exclusion rate and fouling resistance by including a film-forming polymer, a polyoxazoline-based polymer as a first additive and a polyvinylpyrrolidone polymer as a second additive. It is to provide a manufacturing method.

Still another object of the present invention is to provide a porous water treatment membrane having improved water permeability, BSA exclusion rate and fouling resistance, including four layers of a surface layer, a microporous nano sponge layer, a macroporous nano sponge layer, and a spherical particle support layer.

In order to achieve the above object, the present invention According to one feature of the invention 1) preparing a dope solution by mixing a polyvinylidene fluoride or polysulfone film-forming polymer and a polyoxazoline-based polymer mixture as a first additive in a solvent 2) applying the dope solution on a porous support and 3) it provides a method for producing a porous membrane comprising the step of preparing a hollow fiber membrane or a flat membrane by contacting the porous support coated with the dope solution to the external coagulation solution.

The polyvinylidene fluoride film forming polymer is any one selected from the group consisting of polyvinylidene fluoride (PVDF) alone and the polyvinylidene fluoride (PVDF) copolymer having a weight average molecular weight of 10,000 to 1 million. The polysulfone film-forming polymer is at least one selected from the group consisting of polysulfone and polyisulfone having a weight average molecular weight of 10,000 to 1 million.

In addition, polyvinylpyrrolidone which is a second additive may be further added to the first additive when preparing the dope solution in step 1).

The polyoxazoline polymer as the first additive is any one or more selected from the group consisting of polyoxazolines, polyalkyloxazolines and polyaryloxazolines having a weight average molecular weight of 10,000 to 1 million, and the polyalkyloxazolines The alkyl group in is a methyl, ethyl, propyl or butyl group, and the aryl group in the polyaryloxazoline is a phenyl group.

Polyvinylpyrrolidone as the second additive has a weight average molecular weight of 50 to 1 million, When the first and second additives are mixed, the weight ratio of the second and first additives is 0.1 to 1.0.

The solvent is any one or more selected from the group consisting of N-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide and dimethyl formamide, The dope solution is composed of 35 to 90% by weight of the solvent and 10 to 65% by weight of the additive and the polymer resin mixture, the weight ratio of the additive / polymer resin in the additive and the polymer resin mixture is 0.1 to 0.7.

Step 1) is carried out at 15 to 160 ℃.

The porous support is a nonwoven or hollow porous support, and the porous support is at least one selected from the group consisting of polyester, polyamide, and polypropylene.

When step 2) is a porous separator supported by a porous support in the form of a nonwoven fabric, the dope solution is cast on the support in the form of a nonwoven fabric maintained at 15 to 30 ° C, and the step 2) is supported by a porous support in the form of a hollow. In the case of a porous membrane, the dope solution is transferred to an outer tube of a double nozzle maintained at 15 to 160 ° C., and then the hollow support is supplied to an inner tube of the double nozzle.

The support is conveyed at a speed of 0.5 ~ 3.5m / min.

After washing the prepared hollow fiber membrane or flat membrane and immersed in 10 to 50% by weight aqueous solution of glycerin, it may further comprise a step of drying them.

Method for producing a porous separator according to another aspect of the present invention, 1) preparing a dope solution by mixing a polyvinylidene fluoride-based or polysulfone-based film-forming polymer and a polyoxazoline-based polymer mixture of a first additive in a solvent ; 2) transferring the dope solution to the outer tube of the double nozzle, and then supplying the internal coagulating solution to the inner tube of the double nozzle; and 3) simultaneously discharging the dope solution and the internal coagulating solution into the coagulation bath containing the external coagulating solution. To produce a hollow fiber membrane.

In step 2), the dope solution is transferred to an outer tube of the double nozzle maintained at 15 to 160 ° C., and the inner coagulating solution is maintained at 15 to 30 ° C. to the inner tube of the double nozzle.

The internal coagulation solution and the external coagulation solution are not selected from the group consisting of water, ethylene glycol, glycerin, and low molecular weight polyethylene glycols having a molecular weight of 1,000 or less, which do not dissolve the additive and the polymer resin mixture, and can be uniformly mixed with the solvent. Which is more than one.

Except for spinning the dope solution in step 2), steps 1) and 3) are the same as the method of manufacturing the porous separator described above.

Furthermore, the present invention is a surface layer formed on the surface of the separator; A microporous nanosponge layer formed under the surface layer and including a plurality of micropores and nanopores having a skin layer; A macroporous nanosponge layer formed under the microporous nanosponge layer and including a plurality of macropores and nanopores having a skin layer; And the macroporous nano sponge layer. It provides a porous separator consisting of a spherical particle support layer formed on the bottom and including a plurality of pores and spherical particles.

The total membrane thickness of the porous membrane is 100 to 400㎛, 0.05 to 0.7% surface layer, 0.7 to 4.5% microporous nano sponge layer, 4.5 to 45% macroporous nano sponge layer and 45 to 60% spherical particles It consists of a support layer.

In the microporous nanosponge layer, the average pore size of the micropores is 1.5 to 10 μm, the thickness of the skin layer is 0.01 to 0.5 μm, and the average pore size of the nanopores is 100 to 1,000 nm. In the macroporous nano sponge layer, the major diameter of the macropores is 10 to 90 μm, the short diameter is 1 to 50 μm, the thickness of the skin layer is 0.01 to 0.5 μm, and the average pore size of the nanopores is 100 to 1,000 nm. The average particle diameter of the spherical particles in the spherical particle support layer is 0.1 to 10㎛, the average pore size is 0.01 to 5㎛.

The separation membrane is a polyvinylidene fluoride-based or polysulfone-based film-forming polymer and a polyoxazoline-based polymer mixture as a first additive; Alternatively, the dope solution including the film-forming polymer and the polyvinylpyrrolidone mixture of the first and second additives is coated on a spinning or porous support to prepare a hollow fiber membrane or a flat membrane.

The first additive is any one or more selected from the group consisting of polyoxazoline, polyalkyloxazoline and polyaryloxazoline, the weight of the second additive / first additive when mixing the first additive and the second additive The ratio is 0.1 to 1.0.

The dope solution is composed of 35 to 90% by weight of the solvent and 10 to 65% by weight of the additive and the film-forming polymer resin mixture, the weight ratio of the additive / film-forming polymer resin in the additive and the film-forming polymer resin mixture is 0.1 to 0.7 .

As described above, according to the present invention, the addition of the polyoxazoline-based polymer as the first additive to the dope solution induces the generation of nanopores in regions other than micropores and micropores having a skin layer, macropores having a skin layer, and micropores and macropores. And extended. As a result, the water permeability of the porous membrane was improved, especially the pollution resistance was significantly improved, and the BSA exclusion rate was improved at the same time by forming the skin layer.

In addition, according to the present invention, by adding the polymer mixture of the first and second additives to the dope solution, the pollution resistance index was further improved while maintaining the proper pure permeability and the BSA exclusion ratio according to the additive mixing ratio.

In addition, the present invention provides a well-dispersed spherical particle support layer that is not aggregated by adding the first additive and the second additive polymer mixture to the dope solution, thereby improving the water permeability and rejection rate while maintaining the mechanical strength appropriately.

Hereinafter, the present invention will be described in more detail.

Method for producing a porous membrane according to the first embodiment of the present invention 1) preparing a dope solution by mixing a polyvinylidene fluoride-based or polysulfone-based film-forming polymer and a polyoxazoline-based polymer mixture of the first additive in a solvent step; 2) applying the dope solution onto the porous support, and 3) contacting the porous support on which the dope solution is applied to an external coagulation solution to produce a hollow fiber membrane or a flat membrane.

First, step 1) will be described. Step 1) is a process of mixing a polyvinylidene fluoride-based or polysulfone-based film-forming polymer with a polyoxazoline-based polymer as a first additive in a solvent to form a dope solution. The film-forming polymer, a first additive, and a solvent It consists of.

As the polyvinylidene fluoride film-forming polymer, polyvinylidene fluoride (PVDF) alone or polyvinylidene fluoride (PVDF) copolymer may be used, but the use of a single polymer such as polyvinylidene fluoride (PVDF) This is more preferable. In addition, the polysulfone-based film-forming polymer can be used both polysulfone and polyisulfone. The molecular weight of the polyvinylidene fluoride and polysulfone-based film forming polymer is 10,000 to 1 million, preferably 20,000 to 800,000 weight average molecular weight. When the molecular weight of the film-forming polymer is less than 10,000 weight average molecular weight, there is a problem in film forming property due to low viscosity, and when the molecular weight exceeds 1 million weight average molecular weight, film forming is difficult due to high viscosity, which is not preferable.

The first additive is a polyoxazoline-based polymer that serves to induce the generation and expansion of nanopores, micropores and macropores. Specifically, the polyoxazoline-based polymer may use one or more selected from the group consisting of polyoxazolines containing hydrogen atoms, polyalkyloxazolines containing alkyl groups, and polyaryloxazolines containing aryl groups, but are not limited thereto. It doesn't work.

Representative alkyl groups usable in the polyalkyloxazolines containing such alkyl groups are methyl, ethyl, propyl or butyl groups, more preferably polyethyloxazolines. Representative aryl groups usable in the polyaryloxazolines containing the aryl groups are phenyl groups, preferably polyphenyloxazolines.

The polyoxazoline-based polymer as the first additive is used in a weight average molecular weight of 10,000 to 1 million, preferably 50,000 to 80 million. If the molecular weight of the first additive is less than 10,000, the hydrophilicity of the membrane is poor, and if the molecular weight is more than 1 million, it is not preferable because of difficulty in film formation and structure expression due to high viscosity.

The dope solution is composed of 35 to 90% by weight of the solvent and 10 to 65% by weight of the first additive and the film-forming polymer resin mixture, more preferably from 60 to 85% by weight of the solvent and 15 to 15% by weight of the first additive and the film-forming polymer mixture 40 wt%.

In the mixture of the first additive and the film-forming polymer resin, the weight ratio of the first additive / film-forming polymer resin is 0.1 to 0.7. If the content of the first additive and the film-forming polymer is less than 10% by weight, it is impossible to prepare a continuous film due to low viscosity, and if it exceeds 65% by weight, it is difficult to prepare the film due to the high viscosity of the dope solution. In addition, when the weight ratio of the first additive / film forming polymer is less than 0.1, hydrophilicity is hardly imparted, and when it is 0.7 or more, film forming and preferable structure expression are difficult.

Furthermore, the first additive may be substituted with a part of polyvinylpyrrolidone which is a second additive. The polyvinylpyrrolidone is the most commonly used hydrophilic polymer, and the water permeability and fouling resistance can be controlled by mixing with the first additive as it improves the fouling resistance of the membrane due to its hydrophilic characteristics and reduces the average pore. . Polyvinylpyrrolidone which is the second additive is used in an amount of 50 to 1 million, preferably 10,000 to 800,000 weight average molecular weight. If the molecular weight of the polyvinylpyrrolidone is less than 5,000, there is a problem in controlling the membrane structure. If the molecular weight exceeds 1 million, the water permeability decreases rapidly, which is not preferable.

At this time, the weight ratio of the second additive / the first additive when mixing the first additive and the second additive is preferably 0.1 to 1.0. If the weight ratio is less than 0.1, there is a problem of low BSA exclusion rate or fraction molecular weight, and if it is more than 1.0, the water permeability is low, which is not preferable. In addition, the weight ratio of the first additive and the second additive mixture / film forming polymer resin is the weight ratio of the first additive / film forming polymer resin because the first additive is replaced with the mixture of the first and second additives. Such as 0.1 to 0.7.

At this time, the solvent is a solvent that can be uniformly dissolved up to 100% by weight of the polymer resin and up to 100% by weight of additives at the temperature of 15 to 160 ℃ without the formation of a precipitate as N-methylpyrrolidone One or more selected from the group consisting of, dimethylacetamide, dimethyl sulfoxide and dimethylformamide may be used, but is not limited thereto.

Next step 2) will be described. In step 2), the support usable as the step of applying the dope solution prepared in step 1) onto the support is a nonwoven fabric and a hollow support.

In this case, in the case of a porous separator supported by a porous support in the form of a nonwoven fabric, the dope solution is cast on the support in the form of a nonwoven fabric maintained at 15 to 30 ° C.

When the step 2) is a porous separator supported by a hollow porous support, the dope solution is transferred to an outer tube of a double nozzle maintained at 15 to 160 ℃, and then the hollow support on the inner tube of the double nozzle To supply.

The nonwoven and hollow supports may be selected from polyesters, polyamides and polypropylenes, with the use of polyesters being more preferred. The support is preferably transported to a coating bath containing an inner tube of a double nozzle or a dope solution at a speed of 0.5 to 3.5 m / min, the lower the coating speed if the transport speed of the support is less than 0.5 m / min problems in productivity On the contrary, when the feed rate exceeds 3.5 m / min, the coating thickness becomes thin, which is not preferable.

The following 3) steps are explained. Step 3) is a step of preparing a hollow fiber membrane or a flat membrane by contacting the dope solution prepared in step 2) to the external coagulation solution, the external coagulation solution is substantially a mixture of the pore-forming agent and the polymer resin It can be mixed uniformly with the solvent without dissolving at all, preferably any one or more selected from the group consisting of water, glycerin, ethylene glycol and low molecular weight polyethylene glycol having a molecular weight of 1,000 or less can be used, but is not limited thereto. .

In addition, the present invention may further include a washing process to remove the organic matter, including the solvent remaining in the membrane. The use of water as the washing liquid is preferred, and the washing time is not particularly limited. At least 1 day to 5 days are preferred. In addition, the present invention may include the step of immersing the washed hollow fiber membrane and the non-woven form of the support in an aqueous solution of glycerin 10 to 50% by weight, followed by drying in the air, the immersion and drying period is not particularly limited, but one day or less Do.

A second embodiment of the present invention is a hollow fiber membrane without a support, comprising: 1) a mixture of a polyvinylidene fluoride-based or polysulfone-based film-forming polymer and a polyoxazoline-based material as a first additive; Or preparing a dope solution by mixing the film-forming polymer and a mixture of polyvinylpyrrolidone, which is the first and second additives, in a solvent. 2) After transferring the dope solution to the outer tube of the double nozzle, Supplying an internal coagulation solution to the inner tube of the nozzle; and 3) discharging the dope solution and the internal coagulation solution into a coagulation bath including an external coagulation solution at the same time to produce a hollow fiber membrane.

That is, the characteristic of the second embodiment of the present invention is that the dope solution is spun without a support in the second step of the first embodiment.

In the absence of a separate support, the preparation of the membrane can be referred to the contents of the Journal of Membrane Science Vol. 1, 2007 published and the Basic Principles of Membrane Technology (Kluwer Academic), published 1992.

On the other hand, since the second embodiment is substantially the same as described in the first embodiment except that the support is not used in step 2) will be described below with respect to the surface different from the first embodiment.

Since step 1) is the same as step 1) of the first embodiment, the detailed description of the first embodiment is referred to.

In step 2), unlike the first embodiment, a support is not used, and the dope solution prepared in step 1) is transferred to an outer tube of a double nozzle maintained at 15 to 160 ° C., and an inner tube of a double nozzle is provided. The internal coagulating solution is maintained at 15 to 30 ℃.

The internal coagulating solution may be uniformly mixed with the solvent without substantially dissolving the additive and the film-forming polymer resin mixture, and preferably comprises water, glycerin, ethylene glycol and low molecular weight polyethylene glycol having a molecular weight of 1,000 or less. One or more selected from the group may be used, but is not limited thereto.

Furthermore, the present invention provides a porous separator including a microporous nanosponge layer and a macroporous nanosponge layer, which will be described with reference to FIGS. 2 to 4. Specifically, the surface layer 100 formed on the surface of the separator; A microporous nanosponge layer 200 formed under the surface layer and including a plurality of micropores 20 and nanopores 10 having a skin layer 110; A macroporous nanosponge layer 300 formed under the microporous nanosponge layer and including a plurality of macropores 30 and nanopores 10 having a skin layer 110; And the macroporous nano sponge layer. A spherical particle support layer 400 formed below and including a plurality of pores and a plurality of spherical particles 40 dispersed without aggregation; It provides a porous separator comprising a. A feature of the present invention is the enlargement of the microporous nanosponge layer 200 having the skin layer 110 and the nanopores 10 and the macroporous nanosponge layer 300 having the skin layer 110 and the nanopores 10. In the formation of a spherical particle support layer with suppressed formation and aggregation of

The surface layer 100 is formed at the interface where the dope solution and the external coagulation solution first meet, and occupy 0.05 to 0.7% of the total thickness of the porous separator 100 to 400 μm from 0.1 to 1.5 μm from the surface.

The microporous nanosponge layer 200 is located below the surface layer, a plurality of micropores 20 having an average pore size of 1.5 to 10㎛ and a skin layer 110 of 0.01 to 0.5㎛ thickness formed on the surface of the micropores and It is composed of a plurality of nanopores 10 having an average pore size of 100 to 1,000nm formed in portions other than the micropores. In this case, the microporous nanosponge layer 200 occupies 0.7 to 4.5% of the total thickness of the porous separator, and the water permeability, rejection rate, and fouling resistance are improved by the expansion of the microporous nanosponge layer 200. .

The macroporous nanosponge layer 300 is formed under the microporous nanosponge layer 200 and is formed on the surface of the macropore 30 and a plurality of macropores 30 having an average pore diameter of 10 to 90 μm and a short diameter of 1 to 50 μm. Skin layer 110 having a thickness of 0.01 to 0.5㎛ and a plurality of nanopores 10 having an average pore size of 100 to 1,000nm formed in portions other than the macropores. At this time, the macroporous nano sponge layer 300 occupies 4.5 to 45% of the total thickness of the porous membrane, the number of pores having the skin layer 110 is significantly increased due to the generation of the macroporous nano sponge layer 300 The permeability and BSA excretion rate are increased and hydrophilicity is maintained even during long time operation of the separation membrane, so that the water permeability is not reduced and the pollution resistance is improved.

The spherical particle support layer 400 is located under the macroporous nanosponge layer 300, and the spherical particle support layer has a thickness of 100 to 130 μm and occupies 45 to 60% of the total thickness of the porous separator. At this time, the average particle diameter of the spherical particles 40 is 0.1 to 10㎛ and the average pore size in the spherical particle support layer is 0.01 to 5㎛.

Spherical particles are produced depending on the type of solvent added and the temperature difference. The biggest influence is temperature. The spherical particles of the present invention are mainly produced by crystallization of a polyvinylidene fluoride-based polymer, which is a crystalline polymer, and can control the size and growth of the spherical particles by spinning temperature and solution preparation temperature.

The four layers can be adjusted according to the mixing ratio of the film forming polymer, the additive and the solvent used, due to the interaction such as strong hydrogen bonding between the additive and film forming polymer remaining in the film. In particular, as the amount of the first additive is increased, the area of the microporous and nanoporous sponge layers increases and the area of the spherical particle support layer decreases.

The introduction of the first additive, which is a feature of the present invention, induces and expands the generation of micropores and macropores having a skin layer in the membrane structure, as well as generating a nanopore in a portion other than the pores. It is possible to increase the water permeability under molecular weight. In addition, the introduction of the first additive delays the formation of spherical particles and induces formation of spherical particles that are well dispersed without aggregation, thereby improving the durability of the membrane and the BSA excretion rate.

The porous membrane including four layers of the surface layer, the microporous nanosponge layer, the macroporous nanosponge layer, and the spherical particle support layer may be manufactured according to the manufacturing method according to the first embodiment or the second embodiment, but It is not limited and may be manufactured by other methods.

In addition, the average pore size of the porous separator of the present invention depends on the content of the first additive or the mixture of the first and second additives, the extraction time, and the composition of the extraction solvent, and the above structural definition does not limit the present invention. The pure water permeability of the prepared porous separator of the present invention has a feature of maintaining hydrophilicity even during long time operation so as not to reduce the pure water permeability.

Hereinafter, the present invention will be described in detail with reference to examples.

The following examples are merely illustrative of the present invention, but the scope of the present invention is not limited to the following examples.

< Example 1 >

Polyethyloxazoline (POXz, Aldrich Co., Ltd.) as the first additive in a mixture containing 75 wt% of solvent N, N-dimethylacetamide (DMAC) and 20 wt% of polymer polyvinylidene fluoride (Solvay, Mw: 304,000) Mw: 500,000) 5 wt% was added to prepare a dope solution. Bubbles contained in the prepared dope solution were removed using a vacuum pump, and then the dope solution was transferred to a double nozzle maintained at 80 ° C. with a diameter of 1.9 mm and an external diameter of 2.5 mm using a gear pump. Thereafter, the hollow fiber membrane coated on the support was prepared by continuously precipitation in water of room temperature, which is an external coagulation solution. At this time, the solution discharge amount was 1.5CC / min, a hollow annular support of polyester material was used. Subsequently, the hollow fiber membrane passed through the external coagulation solution was continuously transferred to the atmosphere for 30 seconds, immediately wound up through a winding bobbin immersed in water, and then removed in the water washing tank to remove more remaining organic solvent. Washed for 96 h. The completely washed hollow fiber membrane was immersed in 50% by weight aqueous solution of glycerin for 24 hours, and dried at room temperature.The hollow fiber membrane with an inner diameter of 0.6 mm and an outer diameter of 1.8 mm had an effective length of 10 cm, and the membrane area was 0.002 m. ^{A two-} person separator was prepared.

< Example 2 >

A separation membrane was prepared in the same manner as in Example 1 except that 10 wt% of the first additive polyethyloxazoline and 70 wt% of the solvent N, N-dimethylacetamide (DMAC) were spun at room temperature. Prepared.

< Example 3 >

5 wt% of the first additive polyethyloxazoline, 5 wt% of the second additive polyvinylpyrrolidone, and 70 wt% of the solvent N, N-dimethylacetamide (DMAC), except that the dope solution was spun at room temperature. In the same manner as in Example 1, a separator was prepared.

< Example 4 >

3 wt% of the first additive polyethyloxazoline, 7 wt% of the second additive polyvinylpyrrolidone, and 70 wt% of the solvent N, N-dimethylacetamide (DMAC), except that the dope solution was spun at room temperature. In the same manner as in Example 1, a separator was prepared.

< Example 5 >

In order to contaminate the separator prepared in Example 1, it was immersed in an aqueous 1000 ppm humic acid solution at room temperature for one month.

 < Example 6 >

In order to contaminate the separator prepared in Example 4, it was immersed in 1,000 ppm aqueous humic acid solution at room temperature for one month.

< Comparative Example 1 >

Without the use of additives, A separation membrane was prepared in the same manner as in Example 1, except that 80 wt% of the solvent N, N-dimethylacetamide (DMAC) was used.

< Experimental Example 1 >

For the separators prepared in Examples 1 to 5 and Comparative Example 1, the physical properties as shown in Table 1, Table 2 and Table 3.

1.Permeability Measurement

Pure water at room temperature was supplied to one side of the separation membrane by using a dead-end method at 2.0 atm for the prepared separation membrane, and the amount of water permeated was measured and converted into unit time, unit membrane area, and permeation rate. It was.

2.BSA exclusion rate measurement

Bovin Serum Albumin (BSA; Aldrich, Mw 66,000) was dissolved in pure water at room temperature to prepare a 1000 ppm aqueous solution. The aqueous solution was supplied at a pressure of 2.0 kg / cm ² to one side of the prepared membrane, and the BSA concentration dissolved in the permeated aqueous solution and initially supplied raw water was measured using an ultraviolet spectrometer (Varian, Cary-100). . Then, the exclusion rate was determined by converting the relative ratio of the absorption peaks measured at the wavelength of 278 nm into percentage using the following equation.

(1)

Percentage Blocked (%) = (Stock Concentration-Permeate Concentration) ÷ Stock Concentration X100

3. Pollution resistance evaluation

The stain resistance evaluation was evaluated by the following formula as reported in the literature. (Separation and Purification Technology, 54, 220 (2007)

(Equation 2)

Pollution resistance index (R) = normal state (BSA solution permeability / pure water permeability) X100

In Equation (2), the larger the R value, the higher the pollution resistance.

Furtherance radiation
Temperature
(℃) Pure Permeability
(ℓ / m ² hr) BSA Exclusion Rate
(%) Membrane structure Pollution Resistance Index, R Example 1 PVDF / POXz /
DMAC
20/5/75 80 843 83.5 Surface layer
Skin layer
Microporous Nano Sponge Layer
Giant Pore Nano Sponge Floor
Spherical Particle Support Layer 61.7 Comparative Example 1 PVDF / DMAC
20/80 80 12 98.8 Surface layer
Microporous Support Layer
Spherical Particle Support Layer 1.3

1 and 3, the result of Example 1 containing the polyoxazoline as a first additive, when compared to Comparative Example 1 does not contain a first additive, the outer surface of the micropores Skin layer was generated, it can be seen that the nano-sized pores are generated in the portion other than the microporous nanoporous layer and the micropores and macropores having a skin layer. In addition, the BSA excretion rate was improved with the creation of the skin layer, and the water permeability and fouling resistance index of the membrane were significantly improved through the expansion of the micropores, the formation of the macroporous nano sponge layer, and the dispersion of the spherical particles. In the case of Comparative Example 1, the high BSA exclusion rate is judged to be due to the formation of a very thick surface layer, while the proper exclusion rate of the present invention is related to the formation of the spherical particle layer in addition to the formation of the skin layer.

The skin layers and nanopores of the microporous nanosponge layer and the macroporous nanosponge layer are shown in FIG. 4.

Furtherance radiation
Temperature
(℃) Pure Permeability
(ℓ / m ² hr) BSA Exclusion Rate
(%) Membrane structure Pollution Resistance Index, R Example 2 PVDF / POXz /
DMAC
20/10/70 Room temperature 1526 48.5 Surface layer
Skin layer
Microporous Nano Sponge Layer
Giant Pore Nano Sponge Floor
Spherical Particle Support Layer 28.5 Example 3 PVDF / PVP /
POXz / DMAC
20/5/5/70 Room temperature 1487 68.7 Surface layer
Skin layer
Microporous Nano Sponge Layer
Giant Pore Nano Sponge Floor
Spherical Particle Support Layer 28.8 Example 4 PVDF / PVP /
POXz / DMAC
20/7/3/70 Room temperature 1408 74.2 Surface layer
Skin layer
Microporous Nano Sponge Layer
Giant Pore Nano Sponge Floor
Spherical Particle Support Layer 33.2

Examples 2 to 4 are obtained by spinning the dope solution according to the weight percent of the first and second additives at room temperature, the pure permeability increases under the appropriate BSA exclusion rate as the first additive polyoxazoline increases In addition, it can be seen that the contamination resistance index is also improved while maintaining an appropriate BSA excretion rate according to the mixing ratio when the additives are mixed.

Furtherance radiation
Temperature
(℃) Pure Permeability
(ℓ / m ² hr) BSA Exclusion Rate
(%) Membrane structure Pollution Resistance Index, R Example 5 PVDF / POXz /
DMAC
20/5/75 80 803 87.6 Surface layer
Skin layer
Microporous Nano Sponge Layer
Giant Pore Nano Sponge Floor
Spherical Particle Support Layer 66.2 Example 6 PVDF / PVP /
POXz / DMAC
20/7/3/70 Room temperature 1383 79.2 Surface layer
Skin layer
Microporous Nano Sponge Layer
Giant Pore Nano Sponge Floor
Spherical Particle Support Layer 38.6

As shown in Examples 5 and 6, the introduction of the polyoxazoline-based and polyvinylpyrrolidone additives greatly improves the fouling resistance of the membrane even though the membrane has been exposed to contaminants for a long time, thereby greatly reducing the accumulation of organic matter on the membrane surface. This resulted in very good water permeability and BSA exclusion rate.

In addition, as a result of Examples 1 and 5, it can be seen that within the appropriate range, four layers of membrane structures are formed irrespective of the spinning temperature of the dope solution, and there is no difference in effects.

As a result, the present invention prepared a separator having improved water permeability, BSA excretion rate and high fouling resistance index by introducing a polyoxazoline-based polymer as a first additive to a dope solution. In addition, it is possible to appropriately control the performance of the separator by introducing a polyvinylpyrrolidone mixture as a first additive and a second additive into the dope solution to adjust the content of the first and second additives. Accordingly, the porous membrane is very suitable for use in the next generation high efficiency separation process industry, including high concentration wastewater treatment, industrial water treatment and drinking water treatment.

1 is an electron scanning microscope photograph of a porous hollow fiber without an additive,

Figure 2 is a perspective view schematically showing the whole cross-section of the membrane including the additive according to an embodiment of the present invention,

3 is an electron scanning micrograph of a porous hollow fiber membrane including an additive according to an embodiment of the present invention.

Figure 4 is an electron scanning micrograph of the nanopore and skin layer of the porous hollow fiber membrane including an additive according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: nano pore

20: fine pores

30: giant pore

40: spherical particle

100: surface layer

110: skin layer

150: microporous support layer

200: microporous nano sponge layer

300: giant porous nano sponge layer

400: spherical particle support layer

Claims (33)

delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete 1) preparing a dope solution by mixing a polyvinylidene fluoride film-forming polymer and a polyoxazoline-based polymer as a first additive in a solvent; 2) applying the dope solution onto the porous support; And 3) preparing a hollow fiber membrane or a flat membrane by contacting the porous support coated with the dope solution to the external coagulation solution; A surface layer formed on the surface of the separator; A microporous nanosponge layer formed under the surface layer and including a plurality of micropores and nanopores having a skin layer; A macroporous nanosponge layer formed under the microporous nanosponge layer and including a plurality of macropores and nanopores having a skin layer; And The macroporous nano sponge layer A polyvinylidene fluoride-based porous separator, characterized in that consisting of; spherical particle support layer formed in the lower portion and comprising a plurality of pores and spherical particles. The porous membrane of claim 21, wherein the porous membrane has a total film thickness of 100 to 400 µm, a surface layer having a thickness ratio of 0.05 to 0.7%, a microporous nano sponge layer having a thickness of 0.7 to 4.5%, and a large diameter of 35 to 45%. The polyvinylidene fluoride-based porous separator, characterized in that consisting of a pore nano-sponge layer and 50 to 60% spherical particle support layer. 22. The method of claim 21, wherein the average pore size of the micropores in the micropore nanosponge layer is 1.5 to 10㎛, the thickness of the skin layer is 0.01 to 0.5㎛, the average pore size of the nanopore is 100 to 1,000nm, macroporous nanosponge The large diameter of the macropores in the layer is 10 to 90㎛ the short diameter is 1 to 50㎛, the thickness of the skin layer is 0.01 to 0.5㎛, the average pore size of the nanopores is 100 to 1,000nm, the average particle diameter of the spherical particles in the spherical particle support layer is The polyvinylidene fluoride-based porous separator, characterized in that 0.1 to 10㎛ and the average pore size is 0.01 to 5㎛. delete The polyvinylidene fluoride-based porous separator according to claim 21, wherein the polyvinylidene fluoride-based porous separator is prepared by further adding polyvinylpyrrolidone as a second additive to the first additive in preparing the first step dope solution. The method of claim 25, wherein the first additive is any one or more selected from the group consisting of polyoxazoline, polyalkyloxazoline and polyaryloxazoline, the second additive when mixing the first additive and the second additive The polyvinylidene fluoride-based porous separator, characterized in that the weight ratio of the / first additive is 0.1 to 1.0. 26. The method of claim 25, The dope solution is composed of 35 to 90% by weight of the solvent and 10 to 65% by weight of the additive and the film-forming polymer resin mixture, the weight ratio of the additive / film-forming polymer resin in the additive and the film-forming polymer resin mixture is 0.1 to 0.7 The polyvinylidene fluoride-based porous separator, characterized in that. 1) preparing a dope solution by mixing a polyvinylidene fluoride film-forming polymer and a polyoxazoline-based polymer as a first additive in a solvent; 2) transferring the dope solution to an outer tube of the double nozzle, and then supplying an internal coagulating solution to the inner tube of the double nozzle; And 3) manufacturing the hollow fiber membrane by discharging the dope solution and the internal coagulating solution at the same time to a coagulation bath containing an external coagulating solution; A surface layer formed on the surface of the separator; A microporous nanosponge layer formed under the surface layer and including a plurality of micropores and nanopores having a skin layer; A macroporous nanosponge layer formed under the microporous nanosponge layer and including a plurality of macropores and nanopores having a skin layer; And The macroporous nano sponge layer A spherical particle support layer formed on the lower part and including a plurality of pores and spherical particles; Polyvinylidene fluoride-based porous separator, characterized in that consisting of. The porous membrane of claim 28, wherein the porous membrane has a total film thickness of 100 to 400 µm, a surface layer of 0.05 to 0.7% of the total film thickness, a microporous nano sponge layer of 0.7 to 4.5%, and a large thickness of 35 to 45% by a thickness ratio. The polyvinylidene fluoride-based porous separator, characterized in that consisting of a pore nano-sponge layer and 50 to 60% spherical particle support layer. 29. The method of claim 28, wherein the average pore size of the micropores in the micropore nanosponge layer is 1.5 to 10㎛, the thickness of the skin layer is 0.01 to 0.5㎛, the average pore size of the nanopores is 100 to 1,000nm, macroporous nanosponge The large diameter of the macropores in the layer is 10 to 90㎛ the short diameter is 1 to 50㎛, the thickness of the skin layer is 0.01 to 0.5㎛, the average pore size of the nanopores is 100 to 1,000nm, the average particle diameter of the spherical particles in the spherical particle support layer is The polyvinylidene fluoride-based porous separator, characterized in that 0.1 to 10㎛ and the average pore size is 0.01 to 5㎛. The polyvinylidene fluoride-based porous separator according to claim 28, wherein the polyvinylidene fluoride-based porous separator is prepared by further adding polyvinylpyrrolidone as a second additive to the first additive in preparing the first step dope solution. 32. The method of claim 31, wherein the first additive is any one or more selected from the group consisting of polyoxazoline, polyalkyloxazoline, and polyaryloxazoline, and the second additive when mixing the first and second additives. The polyvinylidene fluoride-based porous separator, characterized in that the weight ratio of the / first additive is 0.1 to 1.0. 32. The method of claim 31, The dope solution is composed of 35 to 90% by weight of the solvent and 10 to 65% by weight of the additive and the film-forming polymer resin mixture, the weight ratio of the additive / film-forming polymer resin in the additive and the film-forming polymer resin mixture is 0.1 to 0.7 The polyvinylidene fluoride-based porous separator, characterized in that.

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